1. Field of the Invention
This invention relates to crosslinked polymers of vinyl pyrrolidone, and, more particularly, to crosslinked copolymers of vinyl pyrrolidone and a monomer derived from 1-vinyl-3-(E)-ethylidene pyrrolidone (EVP).
2. Description of the Prior Art
Crosslinked polyvinylpolypyrrolidone (PVPP) is widely employed as a clarifying agent in the industrial purification of wine and beer solutions, particularly for the removal by adsorption of organic impurities such as polyphenols, tannins and anthrocyanins which may be present in the aqueous solution. However, this polymer is incapable of removing heavy metal ions, in particular, copper and iron ions, which also contribute to the toxicity and cloudiness of such solutions.
PVPP is made by popcorn or proliferous polymerization of vinyl pyrrolidone (VP) in the presence or absence of added crosslinking agents, as described in U.S. Pat. Nos. 3,277,066; 3,306,888; 3,759,880; 3,933,766; 3,992,562; and 5,391,668, and by F. Haaf et al. in Polymer J. 1701), p. 143-152 (1985), entitled "Polymer of N-Vinyl Pyrrolidone: Synthesis, Characterization and Uses".
Controlled modification of the properties of PVPP may be accomplished by the introduction of comonomers with vinyl pyrrolidone which contain functional or ligand groups capable of preferential binding of copper or iron ions. For example, U.S. Pat. No. 5,094,867 described a copolymer of vinyl pyrrolidone containing 50-99.5% of a ligand-containing comonomer, particularly N-vinyl imidazole, (NVI), which is an amine-containing comonomer, to remove such heavy metal ions. However, the NVI comonomer in this system must be used in very high concentrations to achieve the desired binding effect. In addition, the vinyl pyrrolidone content of this copolymer is much less than for PVPP alone, which reduces the useful properties of the copolymer as a clarifying agent.
Accordingly, it is an object of the present invention to provide a new and improved PVPP copolymer for use in the industrial clarification of aqueous solutions.
Another object herein is to provide a crosslinked PVPP copolymer which includes a heavy metal chelating comonomer for vinyl pyrrolidone, which comonomer is present in small amounts but is effective in completing and removing traces of heavy metals such as copper and iron ions present in aqueous solutions.
A particular object herein is the provision of a vinyl pyrrolidone copolymer which contains a monomer derived from 1-vinyl-3-(E)-ethylidene pyrrolidone (EVP).
Still another object herein is to provide a vinyl pyrrolidone copolymer which contains 3-(2-aminoethyl)-.alpha.-aminoethyl-N-vinyl pyrrolidone (AEAEVP) as comonomer therein.
A further object herein is to provide a proliferous polymerization process for making such copolymers.
These and other objects and features of the invention will be made apparent from the following more particular description of the invention.